Laserfiche WebLink
Water. Contaminant Removed from Excavation Pit 1993 <br /> • C = 3,225 gal x 0 000014 ppm = 0 045 gal TPHG <br /> C = 3,225 gal x 0 000000020 ppb = 0 000064 gal Benzene <br /> MTBE was not analyzed for that data set. <br /> Water Estimated Mass Remaining <br /> Concentration = (soil volume)(porosity n%)(concentration observed), assumed to <br /> represent concentrations remaining in capillary fringe and aquifer <br /> Water ca ill /a uifer March, 2000 data estimated in vicinity of B-1, B-2 and <br /> B-3, area 20' x 20' x 15' thick, <br /> C = V(n) C observed <br /> C = 6,000 ft3 x 0 3 x 7 48 gal/ft x 0 0010152 ppm = 182 gal TPHG. <br /> Benzene was not detected in that data set. <br /> MTBE was not detected in that data set. <br /> . Discussion - Excavated and Residual Contaminant Mass <br /> The calculated estimates indicate that extremely low quantities of residual contaminants are <br /> present both in the soil, capillary fringe and aquifer in the area excavated in 1993 The <br /> range of concentrations suggests that these residuals, were absorbed onto the soil The <br /> predominant contaminant is TPHG and MTBE was not detected in 2000 (and was not a <br /> selected analyte in 1993) The 1993 CAM 17 metal data shows that these trace elements <br /> were present in concentrations which appear typical for the regional geology <br /> The observed soil sample and monitoring data above show that TPHG contaminants (the <br /> most prevalent on-site) are effectively immobile, and concentrations have declined on the <br /> basis of groundwater monitoring data Neither Benzene nor MTBE has been observed in <br /> the monitoring well In our opinion, this further substantiates the conclusion of absorbed <br /> and highly degraded TPHG contaminants These calculations indicate the residual <br /> calculated remaining quantities are muumal <br /> Residual Contaminants Fate <br /> The 1993 soil excavation and pit dewatering removed contaminated soil and groundwater <br /> Perimeter soil samples revealed low concentrations residual contaminants at the capillary <br /> fringe and base of excavation (see Figure 2) A calculated estimate of TPHG and Benzene <br /> show that very low quantities of both contaminants remain in soil and capillary water The <br /> excavation removed low quantities of contaminants from the former tank pit area and <br /> immeidate vicinity It is anticipated that these residual contaminants will degrade with <br /> time through in-site biodegradation processes Groundwater monitoring well data shows <br /> • that concentrations have declined to none detected <br /> Page 5 <br />